Improved Multiport Hybrid DC Circuit Breaker for Multiple Fault Isolation in Multi-Terminal DC Grid

The multiport DC circuit breaker has the advantages of low implementation cost and fast action speed, which is an ideal way to isolate the DC line fault in multiterminal DC grids. However, in extreme cases, multiple faults may occur in the multi-terminal DC grids, and the conventional multiport DC circuit breaker may not have the ability to handle them. To solve this problem, this paper proposes an improved multiport hybrid DC circuit breaker for multiple fault isolation in multi-terminal DC grids. The proposed breaker contains two main breakers, which serve as backup for each other when isolating single fault, thereby improving the operation reliability of the DC circuit breaker; and act cooperatively when isolating multiple faults. Extensive simulations show that the proposed multiport hybrid DC circuit breaker can meet the speed and selectivity requirements of the multi-terminal DC grid no matter whether single fault or multiple faults occur.